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US 8,160,887 B2Granted
Adaptive interpolation in upsampled audio signal based on frequency of polarity reversals
AssigneeD&M Holdings, Inc.
InventorMitsugi Fukushima
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Abstract
Digital audio sample data are adaptively processed for interpolation based on whether the frequency at which the digital audio signal samples reverse polarity is at least equal to a predetermined threshold, the threshold being determined by their sampling frequency. If so, the digital audio signal samples are subjected to zero-order interpolation, with zero-inserting between the samples followed by lowpass filtering; if not, the samples are subjected to Lagrange (spline) interpolation processing.
Claims10
An audio signal output device for outputting based on a digital audio signal, comprising:
- a judging unit for judging a frequency of reversals in polarity of a digital audio signal;
- and
- a selecting unit for switching an output between an output based on a first interpolated digital audio signal obtained by interpolating the digital audio signal by way of a first interpolation processing and an output based on a second interpolated digital audio signal obtained by interpolating the digital audio signal by way of a second interpolation processing in response to a judgment result made by the judging unit;
- and
- wherein the judging unit judges whether or not the frequency of reversals in polarity of the digital audio signal is equal to or larger than a predetermined reference frequency;
- the first interpolation processing comprises Lagrange interpolation processing or spline interpolation processing;
- the second interpolation processing comprises zero-order interpolation processing for, after zero signals are inserted in intermediate portions of sampling points of the digital audio signal, performing a low-pass filter processing with respect to the digital audio signal;
- the selecting unit switches the output to the output based on the second interpolated digital audio signal for cases in which the frequency of reversals in polarity of the digital audio signal is equal to or larger than the predetermined reference frequency;
- and
- the predetermined reference frequency is determined based on a sampling frequency of the digital audio signal.
7 more elements
An audio signal output method, comprising:
- a judging step of judging a frequency of reversals in polarity of a digital audio signal;
- and
- a switching step of switching an output between an output based on a first interpolated digital audio signal obtained by interpolating the digital audio signal by way of a first interpolation processing, and an output based on a second interpolated digital audio signal obtained by interpolating the digital audio signal by way of a second interpolation processing in response to the result;
- and
- wherein the judging step and the switching step are performed by an audio signal output device;
- the judging step includes judging whether or not the frequency of reversals in polarity of the digital audio signal is equal to or larger than a predetermined reference frequency;
- the first interpolation processing comprises Lagrange interpolation processing or spline interpolation processing;
- the second interpolation processing comprises zero-order interpolation processing for, after zero signals are inserted in intermediate portions of sampling points of the digital audio signals, performing a low-pass filter processing with respect to the digital audio signals;
- the selecting step includes switching the output to the output based on the second interpolated digital audio signal for cases in which the frequency of reversals in polarity of the digital audio signal is equal to or larger than the predetermined reference frequency;
- and
- the predetermined reference frequency is determined based on a sampling frequency of the digital audio signal.
8 more elements
Dependencies are inferred from the claim text.